You just have to keep resetting your game over and over again until you find the map you like. Believe me, I had to do it like 30 times before I found one I like. :/
sadly, the maps you get are random. Some are more common than others, but just keep trying, you'll get the river shape you want in the end, and you'll be happy you kept trying. Good luck!
Have a look at all the possible maps, it lets you know what to expect and gives you the probabilities. There is no way to influence the game's random number generator, but it helped me to know what I was looking for when I resetted for over three hours
Unfortunately all the maps are random but I hear that shutting off your 3DS and turning it back on resets the maps but I'm not sure how true that is. I remember I spent weeks trying to find a map I liked.
Unfortunately all the maps are random but I hear that shutting off your 3DS and turning it back on resets the maps but I'm not sure how true that is. I remember I spent weeks trying to find a map I liked.